Carpet and carpet tiles having cushioned backings are well known to those of skill in the art. Such cushioned backed carpet is disclosed, for example in my U.S. Pat. No. 4,522,857 (incorporated by reference). An example of a prior art tufted carpet product is illustrated in FIG. 1A and an example of a prior art bonded carpet product is illustrated in FIG. 1B herein.
In the prior art tufted carpet, a primary carpet fabric 12 is embedded in an adhesive layer 16 in which is embedded a layer of glass scrim or nonwoven material. A foam base composite 19 is likewise adhesively bonded to the adhesive layer 16. In the prior art tufted carpet illustrated in FIG. 1A, the primary carpet fabric 12 includes a loop pile layer 20 tufted through a primary backing 22 by a conventional tufting process and held in place by a precoat backing layer of latex 24 or other appropriate adhesive including a hot melt adhesive or the like. The foam base composite 19 of the prior art tufted carpet product preferably includes an intermediate layer 26 molded to a layer of urethane foam 28 as illustrated.
The bonded carpet product (FIG. 1B) formed according to the prior art employs the same type of foam base composite 19 adhesively bonded by adhesive laminate layers 16. However, the primary carpet fabric 12 has somewhat different components from that of the tufted product in that it preferably comprises cut pile yarns 34 implanted in a PVC, latex, or hot melt adhesive 36 having a woven or nonwoven reinforcement or substrate layer 38 of fiberglass, nylon, polypropylene or polyester.
The practice utilized in forming the product disclosed in my '857 patent and other known products involves preforming and curing the foam base composite 19 of urethane foam and backing material by practices such as are disclosed in U.S. Pat. Nos. 4,171,395, 4,132,817 and 4,512,831, to Tillotson (all incorporated by reference). In the present practice, only after this foam base composite is formed and cured to some degree as a modular component, is it laminated to the carpet base.
As will be appreciated, the cost associated with such modular formation and assembly practices may be reduced by a simplified operation in which a primary carpet fabric, either with or without a stabilizing layer of scrim or the like, is laid directly into a polyurethane-forming composition and thereafter curing the polyurethane. The process can be made even more efficient if the polyurethane-forming composition requires no pre-curing prior to joining the carpet base.
Prior to the present invention, the known processes directed to the application of the polyurethane cushioned backings to fabric substrates have relied on the extremely close control of temperature in both the polyurethane composition and the adjoined fabric layer to effect stability through pre-cure of the polyurethane prior to lamination of the primary carpet to form a composite structure. Such pre-cure has been largely considered necessary in order to yield a stable foam structure to which the primary carpet backing could be applied. The application of heat to the polyurethane composition prior to joinder of the heated fabric backing causes polymer cross linking which has heretofore been thought to be necessary to stabilize the foam mixture to a sufficient degree to prevent the collapse of the foam.
The present invention also provides a particularly simple composite structure amendable to in-situ formation of a stable cushion carpet composite which is not believed to have been previously utilized. Specifically, it has not been previously recognized that a single process could be used to bring all the layers of the cushioned carpet composite together by laying a primary carpet fabric, either with or without some degree of preheat, directly into a mechanically frothed polyurethane-forming composition prior to curing the polyurethane and without an intermediate layer of material.
As indicated, the prior art carpet forming processes typically require the separate formation of a foam base composite comprising a backing layer and a layer of urethane foam. The backing layer is then used as an intermediate layer to which a primary carpet fabric and reinforcing layer can be adhesively bonded.
In the potentially preferred practice of the present invention, the base of the primary carpet fabric is adhesively bonded to a layer of non-woven glass reinforcement material to form a preliminary composite. A puddle of polyurethane-forming composition is simultaneously deposited across a nonwoven backing material. The preliminary composite and the polyurethane-forming composition are thereafter almost immediately brought together with the preliminary composite being laid into, and supported by, the polyurethane-forming puddle. The entire structure is then heated to cure the polyurethane forming composition. The preliminary composite may be slightly heated to about 120.degree. F. to improve heating efficiency although the process may likewise be carried out without such preheating.
It is to be understood that, as with the prior art products, wherein the primary carpet fabric 12 may have different embodiments, the component structure of the primary carpet fabric is not critical to the present invention. Rather it is intended that any primary carpet fabric having a pile-forming portion and a primary base may be utilized as the primary carpet fabric. By "primary base" is meant any single layer or composite structure including, inter alia, the commonly used layered composite of primary backing 22 and latex precoat 24 previously described in relation to the prior art tufted product (FIG. 1A) and the adhesive layer 36 with reinforcement substrate 38 previously described in relation to the prior art bonded product (FIG. 1B). As will be appreciated, the use of polyester in the primary base structure may be desirable due to the eventual heat curing such structure may undergo. Other embodiments as may occur to those of skill in the art may, of course, also be utilized. For example, in the bonded product, the pile forming yarns could be heat tacked to the substrate 38 as disclosed in my copending application Ser. No. 08/091,309 to permit simplified construction of a primary carpet.